Re: [PATCH v3] tty: serial: samsung_tty: loopback mode support
From: Marek Szyprowski <m.szyprowski@samsung.com>
Date: 2022-07-12 14:01:13
Also in:
linux-samsung-soc, linux-serial
On 12.07.2022 02:44, Chanho Park wrote:
quoted
quoted
+ if (mctrl & TIOCM_LOOP) + ucon |= S3C2410_UCON_LOOPBACK; + else + ucon &= ~S3C2410_UCON_LOOPBACK; + + wr_regl(port, S3C2410_UCON, ucon);S3C2410_UCON must be modified at least under the local_irq_save() or port lock, otherwise it breaks kernel console operation on older Exynos SoCs (especially when DMA mode is used). The above read-modify-write sequence should be replaced with the following pattern: if (mctrl & TIOCM_LOOP) s3c24xx_set_bit(port, S3C2410_UCON_LOOPBACK, S3C2410_UCON); else s3c24xx_clear_bit(port, S3C2410_UCON_LOOPBACK, S3C2410_UCON);All the set_mctrl() call can be protected by spin_[un]lock_irq[save/restore] with port->lock. So, I think it is not required.
Right. The problem is elsewhere. You used rd_reg(port, S3C2410_UCON) instead of rd_regl(port, S3C2410_UCON) what always zeroed upper bits. I will send a fix in a few minutes. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel